Fresh Water on Earth

Episcopal Diocese of Virginia

Stewardship of Creation

Conference on Water Sustainability

September 18, 2010

Dudley F. Rochester, M.D.

The Big Picture

The total amount of water on earth is constant

Its distribution varies with climate

97.5% of Earth’s water is in oceans

Fresh Water Locations

Frozen 69.6%

Groundwater 30.1%

Remainder 0.3%

What’s in the Remainder?

Lakes, rivers, wetlands 88%

Atmosphere 11%

In biological matter 1%

Water Cycle

Surface to atmosphere by evaporation, driven by solar energy

Atmosphere to surface by precipitation

Surface to underground by infiltration

Underground discharge back to surface

Sources of Fresh Water

Surface water in lakes & rivers

Shallow groundwater (renewable)

Deep aquifers (non-renewable)

Desalinated salt water (costly in energy and transportation)

Sustainable Water Usage

Annual accessible fresh water is 9200 cubic km; comes to 1350 cubic meters per capita

Total world water withdrawal is 4400 cubic km per year, 48% of accessible

Taking too much water causes environmental damage

Water Supply in Jeopardy

Pollution from sewage; runoff from agriculture & industry

Depletion of deep aquifers

Melting glaciers in Asia & South America

Growing population & demand

What Do We Use Water For?

7% for domestic uses (drink, cook, bathe, sanitation)

22% for industrial uses (manufacture & process materials)

70% for agriculture (grow food & other crops)

Water Status & Per Capita Use

Status m3/year

Water famine < 150

Need to import food < 1000

Adequate 1300-1500

Surplus, export food > 2000

USA average 2700

Fresh Water Supply by Continent

Asia 13,510 km3/year

South America 12,030 “

North America 7,890 “

Africa 4,050 “

Europe 2,900 “

Oceania 2,360 “

Fresh Water Supply Per Capita

Asia 3,900 m3/person/yr

Europe 4,200 “

Africa 5,700 “

North America 17,400 “

South America 38,200 “

Oceania 82,200 “

Lack of Access to Fresh Water

1.1 billion people lack access to safe drinking water

2.2 billion do not have enough water for sanitation

3.1 billion have to carry water to their home (24 gallons, 200 lbs, for 3 miles)

Ancient Conflicts over Water

Lagash vs Umma in 2500 BC; Egypt, Persia, Babylon, Assyria in 612 BC; Athens vs Sparta in 430 BC; Goths vs Rome in 537 AD; China in 1642 AD.

Tactics included diversion of streams, breaching dikes, cutting aqueducts and poisoning cisterns.

Modern Conflicts over Water

India, Pakistan& Kashmir

Israel, Syria, Lebanon & Jordan

Kenya, Sudan, Somalia, Yemen

Cost versus Value of Water

Water is too cheap; it is used unwisely

Average fee for water is $2.30 per 1000 liters (range $0.40 to $5.20)

“…colossal underpricing of water’s full economic and environmental worth” Steven Solomon, 2010

Water Footprints

Commodity Amount liters H2O

Beef kg 15,000

Pork kg 4,800

Coffee liter 900

Tea liter 120

Blue jeans pair 11,000

Paper ream 5,000

Conserve Water

Irrigate parsimoniously

Detect and fix leaks

Save and recycle used or wasted water

Scrimp on bottled water, lawns and meat

Pricing, Fixing, Producing

Price water realistically

Repair aging infrastructure

Increase production (desalination)

Add storage & distribution facilities

Summary: Problems

Accessible water is unevenly distributed across the world

Half the world population live in water-stressed areas

Inadequate water supply engenders conflicts & wars

Summary: Solutions

Reset the price of water

Conserve & reuse water

Find new water sources

Repair old & build new water infrastructure

Domestic Water Requirement

Activity m3/person/year

Drink 1.8

Sanitation 7.3

Bathe 3.5

Prepare food 3.7

Grow food 986

Total 1004